title: Anatomical features associated with water transport in imperforate tracheary elements of vessel-bearing angiosperms.
abstract: OBJECTIVE
  Imperforate tracheary elements (ITEs) in wood of vessel-bearing angiosperms may or may not transport water. Despite the significance of hydraulic transport for defining ITE types, the combination of cell structure with water transport visualization in planta has received little attention. This study provides a quantitative analysis of structural features associated with the conductive vs. non-conductive nature of ITEs.
  
  
  METHODS
  Visualization of water transport was studied in 15 angiosperm species by dye injection and cryo-scanning electron microscopy. Structural features of ITEs were examined using light and electron microscopy.
  
  
  RESULTS
  ITEs connected to each other by pit pairs with complete pit membranes contributed to water transport, while cells showing pit membranes with perforations up to 2 µm were hydraulically not functional. A close relationship was found between pit diameter and pit density, with both characters significantly higher in conductive than in non-conductive cells. In species with both conductive and non-conductive ITEs, a larger diameter was characteristic of the conductive cells. Water transport showed no apparent relationship with the length of ITEs and vessel grouping.
  
  
  CONCLUSIONS
  The structure and density of pits between ITEs represent the main anatomical characters determining water transport. The pit membrane structure of ITEs provides a reliable, but practically challenging, criterion to determine their conductive status. It is suggested that the term tracheids should strictly be used for conductive ITEs, while fibre-tracheids and libriform fibres are non-conductive.
authors.affiliation: Graduate School of Agriculture, Hokkaido University, Sapporo, Japan. pirika@for.agr.hokudai.ac.jp
authors.forename: Yuzou
authors.initials: Y
authors.lastname: Sano
authors.forename: Hugh
authors.initials: H
authors.lastname: Morris
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Shimada
authors.forename: Louis P
authors.initials: LP
authors.lastname: Ronse De Craene
authors.forename: Steven
authors.initials: S
authors.lastname: Jansen
mesh_terms: D001692:Biological Transport; D048429:Cell Size; D002473:Cell Wall / Q000502:physiology / Q000648:ultrastructure; D020285:Cryoelectron Microscopy; D019684:Magnoliopsida / Q000166:cytology / Q000378:metabolism / Q000648:ultrastructure*; D008855:Microscopy, Electron, Scanning; D014867:Water / Q000378:metabolism*
chemical_list: D014867:Water